SIMPLEX: Symbol-Level Information Multiplex

Internet of Things (IoT) heavily relies on wireless communication to interconnect various sensors and hubs. This paper proposes a symbol-level information multiplexing mechanism (SIMPLEX) that exploits link margin in wireless networks to minimize channel underutilization. Multiplexing is achieved by carrying extra information through a type of specially designed symbols inserted. The key enabler of the inserting and detecting such specially symbols is a per-bit channel assessment scheme that hierarchically estimates the error probability of a received symbol. On the GNU SDR testbed experiments, SIMPLEX shows an accuracy of 97% in recognizing the special symbols in demultiplexing. By varying the frequency domain indices of such specially symbols and their positions on I-Q constellation map, SIMPLEX provides a series of multiplexing rates that carry different amount of extra information. We also design an adaptive multiplexing rate selection scheme to dynamically achieve optimal exploitation of link margin upon instant channel conditions, which can find the optimal multiplexing rates over 90% of the time on the testbed. Multiplexing throughput gain has been theoretically derived and empirically validated of high accuracy with only a negligible deviation to experiment results. A throughput gain can be obtained as much as up to 55%.